> f = function(a, x) {
    alpha = a[1]
    beta = a[2]
    -sum(dgamma(x, shape = alpha, scale = beta, log = T))
}

> rx = rgamma(30, shape = 10, scale = 4)

> nlm(f, p = c(8, 2), x = rx)
$minimum
[1] 118.3390

$estimate
[1] 9.032684 4.319789

$gradient
[1] -5.301921e-07 -6.447832e-07

$code
[1] 1

$iterations
[1] 17